WO2007032526A1

WO2007032526A1 - Organic electroluminescent display panel

Info

Publication number: WO2007032526A1
Application number: PCT/JP2006/318469
Authority: WO
Inventors: Ayako Yoshida
Original assignee: Pioneer Corporation
Priority date: 2005-09-15
Filing date: 2006-09-12
Publication date: 2007-03-22
Also published as: TW200721904A

Abstract

This invention provides an organic electroluminescent display panel comprising an organic EL element and a substrate supporting the organic EL element, the organic EL element comprising an organic functional layer including a luminescent layer, which emits λ-wavelength light, and first and second display electrodes holding the organic functional layer therebetween. A composite layer comprising an inorganic material film and an organic material film is provided between the substrate and the organic EL element. The refractive index of the organic material film is smaller than that of the refractive index of the inorganic material film. The optical distance L of the organic material film satisfies the following formula: [Mathematical formula 1] λ2/L ≤ FWHM(PL) wherein PL represents a luminescence spectrum of an organic luminescent material contained in the luminescent layer; and FWHM represents the half value width of the luminescence spectrum.

Description

Description Organic electroluminescence display panel Technical Field

The present invention relates to an organic electroluminescence display panel.

[Prior art]

Conventionally, an organic electroluminescence display panel (hereinafter referred to as an organic EL display panel) using an organic light emitting material having an electroluminescence property as an emission source is known. The organic EL display panel supports an organic electroluminescent element (hereinafter referred to as an organic EL element) in which an organic functional layer having an optical function is sandwiched between an anode and a cathode, and the organic EL element. And a plurality of organic EL elements on the substrate, for example, a matrix ^! It is lined up with a dog.

The anode is made of a material having a high work function such as indium tin oxide (ITO). The cathode is formed using a material having a low work function, that is, ^ based on alkali metal and alkaline earth metal.

The organic functional layer includes functional layers such as a hole injection layer, a positive LH5 transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. The organic functional layer is, for example, a single layer made of an organic compound material and having only a light emitting layer, or a three-layer structure of an organic hole transport layer, a light emitting layer, and an organic electron transport layer, or an organic hole transport layer and a light emitting layer. A two-layer structure of layers, and a laminate in which an electron or hole injection layer or a carrier block layer is inserted between these appropriate layers can be obtained.

In an organic EL device having such a configuration, when as is applied between the anode and the cathode, holes and Electrons are injected into the organic functional layer, and these recombine in the light emitting layer to emit light. Such light is emitted to the outside through a substrate or the like.

In general, red (R), green (G), and blue (B) light emission vectors emitted from organic EL elements have a wide peak width (especially the red spectrum). In display panels, it was difficult to improve color reproducibility using only the light emission spectra of the organic light emitting materials of each color.

Therefore, a technique for forming a resonator structure in an organic EL element is being squeezed (for example, see Patent Document 1: International Publication No. 0 1/395 5 4 Pamphlet IV). Such an organic EL device has a first electrode made of a light reflecting material such as platinum (P t), gold ¹ (A u) or the like on the substrate, a semi-functional layer such as an organic functional layer, magnesium, silver, or an alloy thereof. The transparent reflective layer and the second electrode are stacked in sequence. The resonator structure includes a first electrode, an organic functional layer, and a translucent reflective layer, and an organic function) is a resonance part. Such a resonating section is configured to act as a filter by setting the thickness of the organic functional layer to a predetermined condition, and is configured to cause multiple interference in the vicinity of the wavelength λ of light to be extracted.

However, in the organic EL element having the above-described configuration, the thickness of the resonance part to be a filter must be set for each color to be extracted. In other words, in order to introduce a resonator structure into an organic EL element, the thickness of the organic functional layer is adjusted to the desired wavelength of light so that the peak of the wavelength of light to be extracted matches the peak of interference. Must be set.

As a result, the thickness of the organic functional layer that is optimal for the extracted light does not match the thickness of the organic functional layer in which the electrical characteristics (such as electron and hole injection efficiency) of the organic EL element are optimal. A situation may occur.

If the distance of the resonance part, that is, the thickness of the organic functional layer is not set precisely, Spectral characteristics may change, and the emission intensity of light of a desired wavelength may be reduced. In particular, when the organic functional layer is manufactured by wet processing, it is difficult to control the thickness of the thin film by wet processing compared to dry processing such as vapor deposition. Changes in characteristics are likely to occur.

In order to avoid these problems, it has been proposed to increase the thickness of the organic machine 1 for the bow I: 3 ton 1. However, when the thickness of the organic machine is increased, the electrical characteristics deteriorate, which is not preferable.

Furthermore, even if the separation of the resonance part in the organic EL element is strictly adjusted, it is possible to use a TFT or gas barrier layer provided on the substrate, etc. It was found that the cool characteristics and the spectral characteristics of the light emitted from the display panel do not match. Disclosure of the invention

The object of the present invention is to provide means for solving various problems mentioned above as an example.

An organic EL display panel according to the present invention comprises an organic EL element comprising an organic functional layer including a light emitting layer that emits light of wavelength λ, and first and second display electrodes sandwiching the organic functional layer, and the organic EL element. An organic tanned display panel having a substrate and a composite layer comprising an inorganic material film and an organic material film provided between the substrate and the organic EL element, the organic material film The refractive index of the organic material film is smaller than the refractive index of the inorganic material film, and the optical distance L of the organic material film is

― ≤ F WH M (P L)

It is characterized by satisfying t.

(Where, in the above formula, PL is the emission spectrum of the organic light emitting material contained in the light emitting layer) FWHM refers to the full width at half maximum of the emission spectrum. )

An organic EL display panel according to the present invention comprises an organic EL element comprising an organic functional layer including a light emitting layer that emits light of wavelength λ, and first and second display electrodes sandwiching the organic functional layer, and the organic EL element. An organic EL display panel having a substrate, wherein the organic EL element is sealed by the substrate and a composite layer composed of an inorganic material film and an organic material film, and the organic material film The refractive index of the organic material film is smaller than the refractive index of the inorganic material film, and the optical distance of the organic material film is

ON 2

≤ FWHM (PL)

It is characterized by satisfying.

(Here, in the above formula, PL refers to the emission spectrum of the organic light-emitting material contained in the light-emitting layer, and FWHM refers to the half-value width of the light-emitting spectrum.)

Brief Description of Drawings

FIG. 1 is a cross-sectional view of an organic EL display panel according to the present invention.

Figure 2 shows the interference spectrum of the composite layer in the organic EL display panel according to the present invention (Figure 2 (a)), the internal emission spectrum of the organic EL element (Figure 2 (b)), and the spectrum of the emitted light (Figure 2 (c)). FIG.

Fig. 3 is a chromaticity diagram of an organic EL display panel.

FIG. 4 is a schematic cross-sectional view of a modification of the organic EL display panel according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an organic EL display panel and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

For example, as shown in FIG. 1, the organic EL display panel 1 has a substrate 2 and one of both main surfaces of the substrate 2. And a first inorganic material film 3 provided on the main surface. The substrate 2 is made of a resin substrate made of a resin material such as polycarbonate PC) or a glass substrate. The first inorganic material film 3 is made of an inorganic material such as silicon oxide (S i 0 ₂ ), silicon nitride (S i N _x ), silicon nitride oxide (S i ON), and aluminum oxide (A 1 ₂ 0 ₃ ). It has a light transmission property that turns the light in the visible light region.

An organic material film 4 is provided on the first inorganic material film 3. The organic material film 4 is made of a resin material such as a thermosetting resin or an ultraviolet curable resin. The refractive index of the organic material film 4 is smaller than the refractive index of the first inorganic material film 3. The organic material film 4 may be a functional layer such as a color conversion layer (CCM layer) or a color filter layer. .

The organic material film 4 is formed using a wet coating method such as a spin coating method! In the case of using the ₀ wet method, a liquid thermosetting resin or ultraviolet curable resin before curing is disposed on the first inorganic material film by using a spin coating method, and then the uncured resin film. It is also possible to cure and form an organic material film.

The organic material film includes a koto film formed by a wet method, and is close to an inorganic material, that is, a material soluble in an organic solvent such as polysilazane and silica particles used in a sol-gel method. A film made of a mixed material in which inorganic particles such as the above are mixed and dispersed in a resin material is also included.

On the organic material film 4, a second inorganic material film 5 having substantially the same configuration as the first inorganic material film 3 described above is provided. That is, the organic material film 4 is sandwiched between the first and second inorganic material films 3 and 5, and the composite layer 6 is formed by the first and second inorganic material films 3 and 5 and the organic material film 4 having such a configuration. Is formed.

On the second inorganic material film 5, the first display electrode 7 and an organic compound and a light emitting layer (not shown) An organic EL element 10 is provided in which an organic functional layer 8 including the second display electrode 9 and the second display electrode 9 are sequentially formed.

The first display electrode 7 is made of a conductive material such as, for example, indium tin oxide (ITO), indium aluminating oxide (IZO), or the like.

The organic functional layer 8 is made of an organic compound material and includes a light emitting layer (not shown) that emits light having a wavelength λ. For example, the organic functional layer 8 is a hole injection layer made of copper phthalocyanine.

(Not shown), Ding PD (triphenylamine derivative) made of proton transport layer (not shown), AI q ₃ (aluminum chelate complex) light emitting layer (not shown), Lithium oxide electricity It is good also as a laminated body which consists of a child injection layer (not shown).

The second display electrode 9 is made of a metal material such as aluminum (AI). The light emitted from the organic functional layer 8 of the organic EL element 10 having such a configuration is emitted to the outside through the substrate 2. Although not shown, the organic EL element 10 may be covered and sealed with a member that does not allow gas such as oxygen and moisture to escape, that is, a so-called gas barrier property. Examples of such a member include a sealing film made of an inorganic material such as silicon oxide, silicon nitride, silicon nitride silicon oxide, or a can-sealed plate made of glass or metal having a recess. In the organic L display panel 1 having the above-described configuration, the composite layer 6 has a structure in which the low refractive index organic material film 4 is sandwiched between the first and second inorganic material films 3 and 5 having a high refractive index. The composite layer 6 acts as an interference filter in which the light emitted from the organic functional layer 8 interferes while reflecting between the first and second inorganic material films 3 and 5. That is, The organic EL display panel 1 has a structure in which an interference filter layer is formed outside the organic EL element Ί 0. Note that, in order to simplify the explanation, one organic EL element is shown in FIG. An organic EL display panel with a The organic EL display panel is formed with multiple organic EL elements. May be. The plurality of organic EL elements may be arranged in a matrix, for example, on the substrate. '

In the organic EL display panel 1 as described above, the organic material display 4 will be described in more detail by taking the single-layer organic display panel 1 in which the organic material film 4 is made of a single organic material as an example. Of the light emitted from the organic EL element, λ is the wavelength of the light to be extracted, d is the thickness of the organic material film 4, and n is the refractive index of the organic material film 4. Further, when the optical thickness of the organic material film 4, that is, the optical distance is L,

[Equation 3]

^L = n Xd · · 'formula (l)

Represented as:

Here, the conditions under which light intensifies in the organic material film 4 are:

[Equation 4]

πιλ = 2 nd (m is an integer) · · · · (2)

In addition, the interval between wavelengths to be intensified (Δλ) is λ (m) when the order is m, and λ (m + 1) when the order is (m + 1). ,

2nd

Formula (3)

Become

Substituting m 2ndZX into equation (3),

[Equation 6]

• Formula (4) It becomes.

Here, the full width at half maximum of the emission spectrum is FWHM (PL). (Note that PL refers to the emission spectrum of the organic light-emitting material contained in the light-emitting layer, and FWHM refers to the half-value width of the emission spectrum.) FWHM (PL) It is preferable that a plurality of interference fringes' peaks appear in the composite layer. For example, as shown in FIG. 2, it is preferable that the interference peak of the light strengthening in the organic material film 4 is set to appear at least three including the peak at the wavelength (λ) of the light to be extracted. . That is,

[Equation 7]

厶 λ ≤ FWHM (PL) ·, · (5)

It is preferable that Here, when substituting Equation (4) and converting,

[Equation 8]

≤ FWHM (PL) · · · · Equation (6)

Therefore, a composite layer satisfying such conditions is preferable.

According to the above settings, the central interference peak among the three interference peaks, that is, the peak at the wavelength λ of the light to be extracted (see Fig. 2 (a)) and the internal emission of the light emitted from the organic EL element The spectrum peak (see Fig. 2 (b)) can almost coincide. Therefore, due to multiple interference in the composite layer, the spectrum of the light emitted through the substrate emitted from the panel becomes a spectrum having a peak at or near the wavelength λ of the light to be extracted. (Figure 2 (c)).

In the case of λ ² / Ι_> FWHM (PL), the interference spectrum shows a peak at the extraction wavelength λ even if the organic material film is manufactured with setting = λΖ2. However, Therefore, it is difficult to control the film thickness of the organic material film, and it is difficult to strictly control the thickness of the organic material film, particularly when the organic material film is produced by a wet process such as a spin-collision method. . Accordingly, the organic material film tends to be easily deviated from the predetermined flUl, and accordingly, the peak position of the interference spectrum is easily shifted from the intended position. Furthermore, when the organic material film is thin, the number of peaks in the interference spectrum is small and the interval between peaks is wide. As a result, when the organic material film is thin (λ ² / L> FWH M (PL)), the spectrum of the light emitted from the substrate is the emission intensity at and around the intended wavelength λ. There is a strong tendency to shift the peak position of outgoing light emitted from the substrate to the outside.

In addition, when the organic material film is thin, the interference filter has a high wave selectivity, so the peak width of the light ffiii of the composite layer is narrower than before. As a result, it is emitted from the display channel. The angle dependence of the emission spectrum of the emitted light is increased. In other words, the organic EL display panel color reproduction range H is ensured only in a narrow viewing angle range.

On the other hand, it has been found that satisfying the condition of the above formula (6) reduces the above-mentioned influence and obtains desired characteristics. That is, by increasing J ^ of the organic material film, multiple interference is obtained. As a result, a number of peaks appear in the interference spectrum, and this can reduce the influence of the peak position of the emitted light on the shift. In addition, although the half-value width of each peak is narrow, the distance between adjacent peaks is narrowed so that light of the wavelength between peaks can be transmitted, and even if the peak position slightly deviates from the intended extraction wavelength, It is avoided that the emission intensity significantly decreases at the wavelength λ and in the vicinity thereof.

In addition, since the wavelength selectivity of the interference filter is slowed down, it is possible to obtain a light with a professional spectrum almost in line with the internal emission spectrum from the organic EL device. As a result, the angle dependency of chromaticity is reduced, and the color reproducibility of the OLED display panel can be maintained over a wide viewing angle. The For example, as shown in Fig. 3, when the display surface of the OLED display panel is placed in front and viewed vertically (in this case, the viewing angle is set to 0 degrees), the green (G) emission is changed from 0 degrees to 60 degrees. When the observation angle is changed in 5 degree increments, compared to the case of setting>HWH> FWH (PL) (Fig. 3 (a)), A ² / L ≤ FWH M (PL) ( The range of change in chromaticity is narrower when set to Fig. 3 (b)). In other words, by increasing the film thickness of the organic material film, the angle dependency of the light emitted from the organic EL element on the spectrum is reduced, and an organic display panel having a sufficient color reproduction range over a wide viewing angle can be obtained. Obtainable. The thickness of the organic material film as described above may be set for each color of red (R), green (G), and blue (B). In other words, the thickness of the corresponding organic material film may be set for each organic light emitting element that emits RGB light. The film thickness of the organic material film may be determined in consideration of a phase shift generated when light is reflected at the interface between the organic material film and the inorganic material film, that is, a phase shift. The optical distance L of the organic material film in the composite layer as described above can be obtained by satisfying the condition of the above formula (6). It is more preferable to set it sufficiently smaller than the half width of the light emission spectrum of the light emitting material to be used. For example, the optical distance of the organic material film is

[]

λ ² FWHM (PL)

Γ ^≥ 3 ... ^(?)

You may meet and meet. By satisfying the above equation (7) and setting the optical path length of light in the organic material film to be long, a large number of interference peaks can be observed over the wavelength band of visible light. Even if the thickness of the organic material film is set for one of the eight colors (for example, green), the interference filter having such an interference spectrum is in the wavelength region of other colors. However, it is possible to emit light having a spectrum close to a desired wavelength characteristic due to multiple interference. That is, it is possible to provide a composite layer having a common organic material film for RGB by omitting setting the film thickness of each material color for each RGB color. It can be simplified. This is particularly effective when manufacturing full-color organic EL display panels with organic EL elements arranged in a matrix.

In addition, such a composite layer is effective in that the wavelength of each RGB color can be adjusted with one composite layer, particularly when the organic EL element emits white light and is set to the condition of the above formula (7). It turns out that there is.

When the substrate is made of a glass substrate, the composite layer has an organic material film on a substrate 2 made of glass as shown in FIG. 4, for example, in addition to a three-layer structure in which an organic material film is sandwiched between inorganic material films. The material film 4 is provided directly (this may be a two-layer structure in which the inorganic material film 5 is disposed on the organic material film 4. By the way, in the case of an organic EL device, when it comes into contact with oxygen and other gases and moisture, a so-called dark spot is formed. In particular, when the substrate is a resin substrate, the resin material easily allows gas and moisture to pass therethrough, so that it has a gas barrier property when the organic EL element is supported on the resin substrate. Therefore, the composite layer may have a gas barrier property and may function as a gas barrier film. Therefore, even if the configuration of the organic EL display panel is simple, desired emission characteristics can be obtained while extending the emission lifetime of the organic EL element.

In addition, since the composite layer has a composite structure (high fabrication) using an inorganic material film and an organic material film, the composite layer can have a good gas barrier property. That is, a minute defect called a pinhole is likely to occur in the inorganic material film, and moisture and the like are easily transmitted through the pinhole. The pinhole is formed by providing an organic material film on the inorganic material film. It can be filled with an organic material to prevent such moisture from entering.

Furthermore, the resin substrate may be a flexible film. By making the substrate flexible, a flexible organic EL display panel that is thin and light and has a wide viewing angle range can be obtained.

In the above embodiment, the organic material film is described as being made of a single organic material thin film, but is not limited thereto. For example, the organic material film may be formed by sequentially stacking a plurality of organic thin films, or these organic thin films may be made of different materials.

The composite layer may have any number of layers as long as organic material films and inorganic material films are alternately laminated. Furthermore, although not shown, a conversion layer (C CM layer) is formed between the substrate and the composite layer.

) A color filter layer and a smooth iUi may be provided.

As described above, by providing an interference filter structure outside the organic EL element, light having a desired peak spectrum can be extracted without affecting the electrical characteristics of the organic EL element.

In addition, a wet method such as a spin coating method can be employed in the production of an organic material film that becomes an interference region. As a result, the production time can be shortened and the cost can be reduced. In the above embodiment, the organic EL surface panel is a method of extracting light to the outside through the substrate, which is a so-called “bomission type panel”, but is not limited to this. A so-called top emission type panel may be used in which light is extracted from the opposite side. The top emission type panel includes an organic EL element including an organic functional layer including a light emitting layer that emits light having a wavelength λ, and first and second display electrodes sandwiching the organic functional layer, and the organic EL element. And a substrate to be carried. The organic EL element includes the substrate and an inorganic material. It is sealed with a composite layer made of a film and an organic material film. The composite layer has substantially the same structure as that of the above-described embodiment. The refractive index of the organic material film in the composite layer is smaller than the refractive index of the inorganic material film, and the optical distance L of the organic material film is

[Equation 1 0]

― ≤ F WHM (PL) · · · · · (8)

Is preferably satisfied.

In the above-described embodiment, the composite layer 6 has a refractive index smaller than those of the first and second inorganic material films 3 and 5 and the first inorganic material films 3 and 5, and The case where the organic material film 4 is arranged has been described. However, the intermediate film 4 disposed between the first and second inorganic material films 3 and 5 may be made of an inorganic material. That is, in the composite layer 6, a film (inorganic material film) 4 made of an inorganic material having a refractive index smaller than that of the inorganic material films 3 and 5 may be arranged between the inorganic material films 3 and 5.

In this case, similarly to the above-described embodiment, when the thickness of the inorganic material film 4 is d and the refractive index of the inorganic material film 4 is n, the optical thickness of the inorganic material film 4 (that is, the optical distance) It is preferable that the composite layer 6 is configured so that L satisfies the above formula (6). Furthermore, it is more preferable that the composite layer 6 is configured to satisfy the above formula (7).

As described above, the inorganic material B 奠 4 is made of silicon oxide (S i 0 ₂ ), silicon nitride (S i N _x ), silicon nitride oxide (S i ON), aluminum oxide (A l ₂ 0 ₃ ), etc. An inorganic material that can be used for Jlii light in the visible light region can be used. The inorganic material film 4 can be formed by a method such as vapor deposition, CVD, sputtering, or IP. A method capable of forming a film with less stress is preferable. Especially in the case of the CVD method, the stress of the film to be formed can be controlled and it is easy to form a thick film. preferable. In addition, since the film formed by the CVD method has excellent coverage performance, a composite layer 6 having excellent barrier performance can be formed. Alternatively, the film can be formed by a wet-co-firing type forming method such as sol-gel or polysilazane.

Claims

The scope of the claims

1. an organic electroluminescent element comprising an organic functional layer including a light emitting layer that emits light of wavelength λ, and first and second display electrodes sandwiching the organic functional layer; and carrying the organic electroluminescent element. And an organic electroluminescence table having a substrate, and

Foreword Ε »A composite layer composed of an inorganic material film and an organic material film is provided between the plate and the organic electroluminescent element.

The refractive index of the organic material film is smaller than the refractive index of the inorganic material film,

The optical distance of the organic material film is

[Equation 1]

¾Organic electroluminescence display panel.

(Here, in the above formula, PL refers to the light emission spectrum of the organic light emitting material contained in the light emitting layer, and FWHM refers to the half width of the emission spectrum.)

2. The optical distance! _ Of the organic material film is

[Equation 2]

52

—— ≤ FWHM (PL)

The organic electroluminescence display panel according to claim 1, wherein the board is made of a resin substrate.

3. The organic electroluminescence display panel according to claim 1, wherein the organic material film is sandwiched between the inorganic material films in the composite layer.

4. The organic electroluminescence display panel according to claim 1 or 2, wherein the B >> plate is made of a glass substrate.

5. The organic electroluminescence display panel according to claim 1, wherein the composite layer has a gas barrier property.

6 · an organic electroluminescent element comprising an organic functional layer including a light emitting layer emitting light of wavelength λ and the first and second display electrodes sandwiching the organic functional layer; and carrying the organic electroluminescent element An organic electroluminescence display panel, wherein the organic electroluminescence element is sealed by the substrate and a composite layer comprising an inorganic material film and an organic material film,

• The optical distance of the organic material film is

[Equation 3]

λ ² ''''

― ≤ FWHM (PL)

An organic electroluminescence panel characterized by satisfying the requirements.

7The optical distance L of the organic material film is

[Equation 4]

7. The organic electroluminescence display panel according to claim 6, wherein _ ≤ FWHM (PL) is satisfied.

8. The organic engineering light emitting luminescence display panel according to claim 6 or 7, wherein the organic material film is sandwiched between the inorganic material films in the composite layer.

9. The organic electroluminescence display panel according to claim 6, wherein the composite layer has a gas barrier property.

10. An organic electroluminescent device comprising an organic functional layer including a light emitting layer that emits light having a wavelength λ, and first and second display electrodes sandwiching the organic functional layer, and the organic electroluminescent device And an organic electroluminescent luminescence table having a first and second inorganic material film and a third organic material between the substrate and the organic electroluminescent element. A composite layer made of an inorganic material film is provided,

The refractive index of the third inorganic material film is smaller than the refractive index of the first and second inorganic material films.

The optical distance L of the third inorganic material film is

[Equation 5]

An organic electroluminescent luminescence display panel characterized by satisfying T.

(Here, in the above formula, P L refers to the light emission spectrum of the organic light emitting material contained in the light emitting layer, and FWH M refers to the half width of the emission spectrum.)

1 1. The optical distance L of the third inorganic material film is:

[Equation 6]

3 λ ²

F WHM (PL) The organic electroluminescence display panel according to claim 1, wherein